The present invention relates to semiconductor devices of the carrier package type. More particularly, it relates to a semiconductor device which has its package thinned and its cost lowered and which is made easy of installation, and also to a method of producing the same.
In general, a semiconductor device of the type including a carrier package called a chip carrier can be completely installed merely by placing it directly on a circuit board for installation and connecting the wiring terminals of the circuit board with the external connection terminals of the semiconductor device. Therefore, the semiconductor device of the specified type is effective to facilitate the installing job and to thin the whole apparatus in which the semiconductor device is built, and the demand therefor tends to increase more and more.
Most of the prior art semiconductor devices of this type employ a carrier package of ceramic as shown in FIG. 1. This carrier package 1 is constructed and used as stated below. A recess 3 is formed in the upper surface of a carrier base 2 which is formed by, e.g., the green process of ceramic. A semiconductor element (pellet) 4 is fastened on the inner bottom surface of the recess 3. Leads 6, each of which consists of an inner lead for connection with the pellet and an outer lead for external connection, are formed by such an expedient as metallizing in a manner to extend from the perimeter of the recess 3 to the rear surface of the base. After the pellet 4 and the leads 6 are electrically connected by wires 7, the resultant structure is encapsulated by a cap 8 of metal or ceramic.
With this package, however, since there is a limitation to reduction in the thickness of the green ceramic, reduction in the thickness of the base 2 formed by the lamination thereof is naturally limited, which forms an obstacle to thinning the whole package. Moreover, since the green process referred to above includes many steps, the entire package becomes expensive conjointly with the material cost of the ceramic.
Further, the ceramic is greatly different in the coefficient of thermal expansion from a printed circuit board of a glass epoxy material or the like, which is usually used as a board for installation. Therefore, when the ceramic package is directly secured and connected to the printed circuit board of this type, a stress attributed to the difference of the coefficients of thermal expansion develops between the package and the printed circuit board with a change in temperature, and the connection therebetween is sometimes damaged.
Moreover, such ceramic packages are manufactured individually one by one. It is therefore difficult to perform fully automatically the operations of fastening the pellet 4 onto the base 2, bonding the wires 7, fastening the cap 8, etc. Another disadvantage is that the dimensions of the packages manufactured individually are subject to errors, which render the automation more difficult.